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Kandrashkin YE. Estimation of Heisenberg exchange interaction in rigid photoexcited chromophore-radical compound by transient EPR. J Chem Phys 2024; 160:044306. [PMID: 38284654 DOI: 10.1063/5.0188404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 01/04/2024] [Indexed: 01/30/2024] Open
Abstract
The magnetic field dependence of the spin polarization in a photoexcited rigid chromophore-radical conjugate is theoretically investigated. The excitation of the chromophore-radical conjugate often populates the metastable doublet and quartet states formed by the interactions of the unpaired electrons of the triplet chromophore and the radical. The intensities of the +1/2 ↔ - 1/2 transitions of the doublet and quartet manifolds are sensitive to the ratio jω = 3J/ω0 between the triplet-doublet exchange interaction J and the Zeeman energy ω0. It is shown that the analytical expressions of these intensities previously found for the triplet mechanism of the initial spin polarization can be expanded and applied to a broader class of compounds that may have other intersystem crossing pathways of the depopulation of the excited singlet state of the chromophore. It is also shown that the exchange interaction can be evaluated not only by comparing the electron paramagnetic resonance spectra obtained in different microwave frequency bands but also by comparing the data obtained in the same microwave band but with a shift of the frequency of the resonator. The results obtained broaden the potential applications of the previously proposed approach for analyzing the correlation between the exchange coupling and the distance separating the radical and the chromophore spins, as well as the structure of the bridge connecting their fragments.
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Affiliation(s)
- Yuri E Kandrashkin
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Sibirsky Tract 10/7, Kazan 420029, Russia
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2
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Abstract
Photoexcited organic chromophore-radical systems hold great promise for a range of technological applications in molecular spintronics, including quantum information technology and artificial photosynthesis. However, further development of such systems will depend on the ability to control the magnetic properties of these materials, which requires a profound understanding of the underlying excited-state dynamics. In this Review, we discuss photogenerated triplet-doublet systems and their potential to be used for applications in molecular spintronics. We outline the theoretical description of the spin system in the different coupling regimes and the invoked excited-state mechanisms governing the generation and transfer of spin polarization. The main characterization techniques used to evaluate the optical and magnetic properties of chromophore-radical systems are discussed. We conclude by giving an overview of previously investigated covalently linked triplet-radical systems, and highlight the need for further systematic investigations to improve our understanding of the magnetic interactions in such systems.
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3
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Mayländer M, Nolden O, Franz M, Chen S, Bancroft L, Qiu Y, Wasielewski MR, Gilch P, Richert S. Accessing the triplet state of perylenediimide by radical-enhanced intersystem crossing. Chem Sci 2022; 13:6732-6743. [PMID: 35756510 PMCID: PMC9172295 DOI: 10.1039/d2sc01899c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/10/2022] [Indexed: 12/27/2022] Open
Abstract
Owing to their exceptional photophysical properties and high photostability, perylene diimide (PDI) chromophores have found various applications as building blocks of materials for organic electronics. In many light-induced processes in PDI derivatives, chromophore excited states with high spin multiplicities, such as triplet or quintet states, have been revealed as key intermediates. The exploration of their properties and formation conditions is thus expected to provide invaluable insight into their underlying photophysics and promises to reveal strategies for increasing the performance of optoelectronic devices. However, accessing these high-multiplicity excited states of PDI to increase our mechanistic understanding remains a difficult task, due to the fact that the lowest excited singlet state of PDI decays with near-unity quantum yield to its ground state. Here we make use of radical-enhanced intersystem crossing (EISC) to generate the PDI triplet state in high yield. One or two 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) stable radicals were covalently attached to the imide position of PDI chromophores with and without p-tert-butylphenoxy core substituents. By combining femtosecond UV-vis transient absorption and transient electron paramagnetic resonance spectroscopies, we demonstrate strong magnetic exchange coupling between the PDI triplet state and TEMPO, resulting in the formation of excited quartet or quintet states. Important differences in the S1 state deactivation rate constants and triplet yields are observed for compounds bearing PDI moieties with different core substitution patterns. We show that these differences can be rationalized by considering the varying importance of competitive excited state decay processes, such as electron and excitation energy transfer. The comparison of the results obtained for different PDI–TEMPO derivatives leads us to propose design guidelines for optimizing the efficiency of triplet sensitization in molecular assemblies by EISC. The triplet state of PDI can be sensitized efficiently by radical-enhanced intersystem crossing. A detailed study of several related structures allows us to propose new strategies to optimize triplet formation in materials for optoelectronic devices.![]()
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Affiliation(s)
- Maximilian Mayländer
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Oliver Nolden
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1 40225 Düsseldorf Germany
| | - Michael Franz
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Su Chen
- Department of Chemistry, Center for Molecular Quantum Transduction, Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA
| | - Laura Bancroft
- Department of Chemistry, Center for Molecular Quantum Transduction, Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA
| | - Yunfan Qiu
- Department of Chemistry, Center for Molecular Quantum Transduction, Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA
| | - Michael R Wasielewski
- Department of Chemistry, Center for Molecular Quantum Transduction, Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston IL 60208-3113 USA
| | - Peter Gilch
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf, Universitätsstraße 1 40225 Düsseldorf Germany
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
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4
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Bortolus M, Ribaudo G, Toffoletti A, Carbonera D, Zagotto G. Photo-induced spin switching in a modified anthraquinone modulated by DNA binding. Photochem Photobiol Sci 2019; 18:2199-2207. [PMID: 30838367 DOI: 10.1039/c8pp00586a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
An anthraquinone modified with a nitroxide radical and able to intercalate into DNA has been synthesized to obtain a molecule the spin state of which can be manipulated by visible light and DNA binding. The doublet ground state of the molecule can be photo-switched to either a strongly coupled spin state (quartet + doublet), when isolated, or to an uncoupled spin state (triplet and doublet), when bound to DNA. The different spin state that is obtained upon photoexcitation depends on the intercalation of the quinonic core into double-stranded DNA which changes the conformation of the molecule, thereby altering the exchange interaction between the excited state localized on the quinonic core and the nitroxide radical. The spin state of the system has been investigated using both continuous-wave and time-resolved EPR spectroscopy.
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Affiliation(s)
- Marco Bortolus
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
| | - Giovanni Ribaudo
- Department of Pharmaceutical Sciences, University of Padova, via Marzolo 5, 35131, Padova, Italy
| | - Antonio Toffoletti
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
| | - Giuseppe Zagotto
- Department of Pharmaceutical Sciences, University of Padova, via Marzolo 5, 35131, Padova, Italy
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5
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Megiel E. Surface modification using TEMPO and its derivatives. Adv Colloid Interface Sci 2017; 250:158-184. [PMID: 28950986 DOI: 10.1016/j.cis.2017.08.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 08/09/2017] [Accepted: 08/30/2017] [Indexed: 02/01/2023]
Abstract
This article provides an overview of the methods for surface modification based on the use of stable radicals: 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives. Two approaches are discussed. The first relies on the immobilization of TEMPO moieties on the surface of various materials including silicon wafers, silica particles, organic polymers as well as diverse nanomaterials. Applications of such materials with spin labeled surface/interface, in (electro)catalysis, synthesis of novel hybrid nanostructures and nanocomposites as well as in designing of organic magnets and novel energy storage devices are also included in the discussion. The second approach utilizes TEMPO and its derivatives for the grafting of polymer chains and polymer brushes formation on flat and nanostructure surfaces via Nitroxide Mediated Radical Polymerization (NMRP). The influence of such polymer modification on surface/interface physicochemical properties is also presented.
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Affiliation(s)
- Elżbieta Megiel
- University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland.
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6
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Dyar SM, Margulies EA, Horwitz NE, Brown KE, Krzyaniak MD, Wasielewski MR. Photogenerated Quartet State Formation in a Compact Ring-Fused Perylene-Nitroxide. J Phys Chem B 2015; 119:13560-9. [DOI: 10.1021/acs.jpcb.5b02378] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Scott M. Dyar
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Eric A. Margulies
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Noah E. Horwitz
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Kristen E. Brown
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D. Krzyaniak
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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7
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Colvin MT, Carmieli R, Miura T, Richert S, Gardner DM, Smeigh AL, Dyar SM, Conron SM, Ratner MA, Wasielewski MR. Electron Spin Polarization Transfer from Photogenerated Spin-Correlated Radical Pairs to a Stable Radical Observer Spin. J Phys Chem A 2013; 117:5314-25. [DOI: 10.1021/jp4045012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Michael T. Colvin
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Raanan Carmieli
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Tomoaki Miura
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Sabine Richert
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Daniel M. Gardner
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Amanda L. Smeigh
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Scott M. Dyar
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Sarah M. Conron
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Mark A. Ratner
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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8
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Garbuio L, Antonello S, Guryanov I, Li Y, Ruzzi M, Turro NJ, Maran F. Effect of Orientation of the Peptide-Bridge Dipole Moment on the Properties of Fullerene–Peptide–Radical Systems. J Am Chem Soc 2012; 134:10628-37. [DOI: 10.1021/ja303696s] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Luca Garbuio
- Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova,
Italy
| | - Sabrina Antonello
- Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova,
Italy
| | - Ivan Guryanov
- Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova,
Italy
| | - Yongjun Li
- Department of Chemistry, Columbia University, New York, New York 10027, United
States
| | - Marco Ruzzi
- Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova,
Italy
| | - Nicholas J. Turro
- Department of Chemistry, Columbia University, New York, New York 10027, United
States
| | - Flavio Maran
- Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova,
Italy
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9
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Moons H, Goovaerts E, Gubskaya VP, Nuretdinov IA, Corvaja C, Franco L. W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives. Phys Chem Chem Phys 2011; 13:3942-51. [DOI: 10.1039/c0cp01902j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Colvin MT, Giacobbe EM, Cohen B, Miura T, Scott AM, Wasielewski MR. Competitive Electron Transfer and Enhanced Intersystem Crossing in Photoexcited Covalent TEMPO−Perylene-3,4:9,10-bis(dicarboximide) Dyads: Unusual Spin Polarization Resulting from the Radical−Triplet Interaction. J Phys Chem A 2010; 114:1741-8. [DOI: 10.1021/jp909212c] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Michael T. Colvin
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Emilie M. Giacobbe
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Boiko Cohen
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Tomoaki Miura
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Amy M. Scott
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
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11
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Giacobbe EM, Mi Q, Colvin MT, Cohen B, Ramanan C, Scott AM, Yeganeh S, Marks TJ, Ratner MA, Wasielewski MR. Ultrafast Intersystem Crossing and Spin Dynamics of Photoexcited Perylene-3,4:9,10-bis(dicarboximide) Covalently Linked to a Nitroxide Radical at Fixed Distances. J Am Chem Soc 2009; 131:3700-12. [DOI: 10.1021/ja808924f] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Emilie M. Giacobbe
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Qixi Mi
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael T. Colvin
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Boiko Cohen
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Charusheela Ramanan
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Amy M. Scott
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Sina Yeganeh
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Tobin J. Marks
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Mark A. Ratner
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
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12
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Conti F, Corvaja C, Busolo F, Zordan G, Maggini M, Weber S. Time-resolved EPR investigation of [70]fulleropyrrolidine nitroxide isomers. Phys Chem Chem Phys 2009; 11:495-502. [DOI: 10.1039/b813238k] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Kawai A, Shibuya K. Charge-Transfer Controlled Exchange Interaction in Radical-Triplet Encounter Pairs as Studied by FT-EPR Spectroscopy. J Phys Chem A 2007; 111:4890-901. [PMID: 17518447 DOI: 10.1021/jp067753d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The exchange interaction, J, producing quartet and doublet energy separation in radical-triplet excited molecule encounter pairs, was investigated in solution by measuring chemically induced dynamic electron polarization (CIDEP) created through the radical-triplet pair mechanism. A time-resolved FT-EPR method was utilized to measure CIDEP of galvinoxyl radical by recording FID signals and an absolute magnitude of CIDEP, P(n), was determined for each radical-triplet system by detailed analysis of the time evolution curves of CIDEP. A transient FT-EPR signal phase remarkably depends on the triplet molecule. The signal phase is related to the sign of J value, which is responsible for the radical-triplet pair interaction. Most of galvinoxyl-triplet systems showed normal negative sign. An unusual positive sign was found in some systems characterized by a small energy gap, DeltaG, between the radical-triplet pair and intermolecular charge transfer (CT) states. A theoretical calculation of J value for radical-triplet encounter pairs was carried out by considering exchange integral and intermolecular CT interaction. According to the calculated J value and the diffusion theory for CIDEP magnitude, experimental Pn values were theoretically reproduced as a function of DeltaG. The present results confirm our previously reported CT model explaining the complicated nature of the sign of J value in the galvinoxyl-triplet encounter pairs. According to the proposed model for CT effect on J value and CIDEP results, nature of J value in radical-triplet pairs is discussed.
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Affiliation(s)
- Akio Kawai
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ohokayama, Tokyo 152-8551, Japan.
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14
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Gubskaya VP, Berezhnaya LS, Gubaidullin AT, Faingold II, Kotelnikova RA, Konovalova NP, Morozov VI, Litvinov IA, Nuretdinov IA. Synthesis, structure and biological activity of nitroxide malonate methanofullerenes. Org Biomol Chem 2007; 5:976-81. [PMID: 17340014 DOI: 10.1039/b617892h] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two nitroxide methanofullerenes was synthesized for the first time, and their structures and biological activities studied. It was shown by X-ray single crystal analysis that the methanofullerene with two nitroxide groups forms a 1 : 2 inclusion complex with chloroform and has a nearly tetrahedral (diamond-like) arrangement of fullerene-fullerene interactions in the crystal. For the first time, it has been found that malonate nitroxide methanofullerene in combination with the known anticancer drug cyclophosphamide (CPA) shows high antitumor activity against leukemia P-388.
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Affiliation(s)
- Valentina P Gubskaya
- A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center of the Russian Academy of Sciences, 8 ul. Acad. Arbuzova, 420088 Kazan, Russian Federation
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